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We can also include a mechanism to discretise the MVS in order to obtain
a specific mood tag
M
i
∈ M
τ
. To do so, we include a function of neighbour-
hood
A
i
) (for instance a minimal norm distance function) that returns the
mood tag from the current mood for a specific agent
f
ν
(
A
i
,
f
ν
M −−→ M
τ
:
:
u
i
f
ν
−−−−−→ M
i
We remark that an Emotional Agent System fulfils the requirements put for-
ward at the beginning of the section for the representation of emotions and moods.
4
Conclusion and Discussion
This paper has put forward a formalism for representing emotions and moods,
setting out from the psychological framework of the PAD space. Within our
Mood Vector Space we can manage the emotional behaviour of an agent based
on transitions and relations across a three dimensional space. The algebraic
formulation of the properties and functions facilitates the application in a com-
putational model.
Differently from many other approaches, the MVS approach allows for a homo-
geneous representation of emotional components in a well founded framework that
goes beyond the traditional view of the OCC categories. In addition, the Mood Vec-
tor Space provides the ability to include in the same space emotions and moods,
granting the mathematical tools to manipulate these elements. On this basis, it
supports the transformation and manipulation of dynamically changing emotional
elements, composition of emotions into emotional states, etc. Finally, the decay
and threshold mechanism of the MVS model takes into account the requirements
of psychological findings regarding emotional and temperament dynamics.
The ALMA model [4] is perhaps most similar to our approach. It uses the
OCC model as reference for an agent's emotion prompted by the environment.
These emotions are then transformed into PAD components. The main difference
with our approach is that the ALMA model assumes that the mood movement
is based on a pull-push strategy which takes the centre of the PAD space as
reference and the centre of the emotions elicited as influence on the mood. In
our approach, the PAD space is homogeneous for the transitions, supporting the
psychological concept of accumulation of emotions in our mood. The relevance
of a point in the mood space is according to the distance to the default mood
point derived by the personality, and operations over the mood applied by the
emotions or decay are supported.
MVS has been designed for application in different agent architectures and
domains. It has already been used to model the emotional behaviour of software
agents in a commercial video game [Neverwinter Nights
TM2
][10]. In future work,
we plan to use it as part of an agent architecture for the online video game
Diplomacy [DipGame
3
]. In particular, we aim at exploring the implementation
of multilevel MVS to represent mood in different contexts, e.g. when dealing
with different groups of agents (or “nations”).
2
http://nwn.bioware.com/
3
http://www.dipgame.org/
